1. Field of the Invention
The present invention relates generally to fuel vapor emission control for internal combustion engines. More particularly, the present invention relates to fuel tank fuel vapor emission control for internal combustion engines.
2. Description of the Related Art
Modern transportation vehicles which employ a liquid fuel conventionally also employ for storage of the liquid fuel a fuel tank. Similarly, since most liquid fuels are highly volatile, such a fuel tank typically contains in addition to the liquid fuel a fuel vapor. A concentration of fuel in the fuel vapor within the fuel tank is generally related to the temperature of the liquid fuel within the fuel tank, the amount of air in ullage volume, and the temperature of the fuel vapor within the fuel tank.
While a fuel vapor within a fuel tank does not typically impair operation of a transportation vehicle which is powered by an engine which employs a liquid fuel extracted from the fuel tank, upon refueling of the fuel tank with additional liquid fuel, in a first instance, the fuel vapor present in the fuel tank must of necessity be displaced. Similarly, in a second instance, when refueling the fuel tank with additional liquid fuel there is typically also newly generated additional fuel vapor incident to splashing of the additional liquid fuel which is introduced into the fuel tank. For environmental protection purposes and for economic reasons, it is desirable for such displaced fuel vapor and newly generated fuel vapor not to be released into the atmosphere.
Various apparatus, systems and methods have been disclosed within the art of fuel system design for attenuating, upon refueling of a fuel tank, release of a fuel vapor into the atmosphere. Typical in that regard are apparatus, systems and methods which employ either or both: (1) valving schemes to redirect displaced fuel vapors and newly generated fuel vapors in a fashion such as to avoid release into the environment; and (2) sealing means to attenuate, in a first instance, generation of fuel vapors. Representative examples of such apparatus, systems and methods are disclosed within U.S. Pat. No. 4,836,835, U.S. Pat. No. 4,898,395, U.S. Pat. No. 4,944,779, U.S. Pat. No. 4,977,936, U.S. Pat. No. 5,056,570, U.S. Pat. No. 5,404,906 and U.S. Pat. No. 5,462,100, all of which are incorporated herein fully by reference.
While any of the foregoing apparatus, systems and methods provides upon refueling of a fuel tank with a liquid fuel an attenuated displaced fuel vapor release into the atmosphere and/or an attenuated newly generated fuel vapor release into the atmosphere, such desirable result is often achieved only with particularly complicated piping and valving schemes, or with an otherwise incomplete attenuation of fuel vapor release into the atmosphere.
There thus exists within the art of fuel system design a continuing need for comparatively simple apparatus, systems and methods for more completely attenuating upon refueling of a fuel tank release of a fuel vapor into the atmosphere.
It is towards that object that the present invention is directed.